1. Technical Field of the Invention
The present invention relates to an intake system of an internal combustion engine, hereinafter referred to as an engine.
2. Description of the Related Art
In conventionally known intake systems, a passage member for forming the intake passage along with an intake pipe is inserted into a peripheral wall of the intake pipe in the radial direction for assembly. Among examples of the passage member is a throttle body which supports a throttle valve for opening and closing the intake passage.
In an intake system disclosed in Japanese Patent Laid-Open Publication No. Hei 10-103089 (1998), the passage member or throttle body is inserted through an insertion opening formed in the peripheral wall of the intake pipe, and the rear end of the throttle body in the direction of insertion is undetachably fixed to a part of the peripheral wall near the insertion opening. Furthermore, the front end of the throttle body in the direction of insertion is fastened to the peripheral wall by screws. The throttle body might vibrate in directions perpendicular to the axis of the direction of insertion due to collision of the intake air flowing through the intake passage, whereas the unstable front end of the throttle body is securely screwed to suppress the vibrations. The suppression of the vibrations of the throttle body prevents a seal member arranged at the seam between the peripheral wall of the intake pipe and the throttle body from wearing.
When the front end of the throttle body in the direction of insertion is fastened to the peripheral wall of the intake pipe by the screws, however, the screwing of the screw members causes a plastic deformation of the throttle body with a drop in the dimensional accuracy of the bore and the like. In addition, the screw fastening increases the parts count and complicates the assembling operation with an inevitable increase in cost.